The present invention is directed to a soil separator for a dishwasher and particularly an arrangement between a soil separator chamber and a soil accumulator chamber which provides an improved apparatus and method for collecting and filtering soil from dishwasher water.
A known arrangement for removing soil from dishwasher water is described in U.S. Pat. No. 5,165,433. This apparatus includes a combination motor-pump and soil separator assembly. The motor-pump assembly includes a wash impeller, which operates within a pump cavity located within the soil separator. As the impeller operates in a wash or rinse mode, a swirling motion is created in the wash liquid passing through the pump cavity, thereby creating a centrifugally sampled annular layer of wash liquid on the annular interior wall. A portion of the wash liquid having a high concentration of entrained soil (food particles, etc.) passes over an upper edge of the annular interior wall and into an annular guide chamber.
Wash liquid from this guide chamber travels to an annular soil collection chamber at a high flow rate. This high flow rate is achieved by use of a relatively small aperture located in a lower portion of the annular wall separating the guide chamber and the soil collection chamber. Upon entering the soil collection chamber, wash liquid flows outwardly and upwardly through a screen which separates the water from the soil. The wash liquid is prevented from draining out of the soil collection chamber by a ball check valve seated within a drain port. The screen contains an annular arrangement of fine mesh filters, which prevent soil particles entrained in the wash liquid from reentering the dishwasher space. The cleansed wash liquid returns to the dishwasher floor where it is picked up by the motor driven pump for recirculation within the dishwasher.
Typically, the apparatus such as described above allows water to pass through the hole between the guide channel and the collector chamber at a rate of about 4 gallons per minute. This flow rate can cause the heavily concentrated mixture of soil and water within the accumulator chamber to be agitated, preventing soils from readily settling. With this flow rate and configuration, there may be a tendency for the mechanical filter to clog even though back wash nozzles for spraying the filter from above are provided. Collecting soil at these flow rates cause filter screens with a 0.0049 inch mesh to have a tendency to clog. It was necessary to increase screen mesh to 0.0079 inch to prevent this clogging. However, the larger mesh screen allowed soils of larger particle size to escape through the screen and may be seen as xe2x80x9cgritxe2x80x9d on the dishes.
It is an object of the present invention to provide a dishwasher soil collection system which is compatible with a high flow rate soil removal dishwasher while at the same time allowing for adequate screening of soil in the dish water return to the dish compartment in a recirculating dish water system. It is an object of the invention to provide a more efficient method of soil collection and retention while reducing water and energy usage.
The objects are inventively achieved in that an annular soil separator wall is provided around the dish washer pump for accumulating solids by centrifugal action, a soil guide channel is provided surrounding the separator wall, and a shallow soil accumulator channel or xe2x80x9cscreening channelxe2x80x9d, substantially annular, is arranged beneath the filter screen surrounding the soil guide channel. The soil accumulator channel is flow connected to the guide channel by a vertical tube at a first closed end of the channel and the channel surrounds the guide channel to an open channel end which empties, to an accumulator sump having a drain port closed by a ball check valve. Water and soil proceed around the accumulator channel, soil is retained beneath the filter screen and water proceeds through the filter screen. Back wash nozzles are provided to wash the filter screen of soil from a dish compartment side of the filter screen. Thus, by directing inlet water from the guide channel to the shallow accumulator channel, the inside of the filter screen is washed by the water, while the outside of the screen is washed by the backwash nozzles above. Therefore, food particles which are temporarily dislodged from the screen by the backwash nozzles may not immediately return to the screen after the backwash nozzle passes, due to the direction of flow on an inside surface of the filter screen from the water flowing inside the accumulator channel.
Inlet water flow into the accumulator channel is directed in a circulatory path and kept in the shallow accumulator channel in close proximity with the screen. As particles are dislodged by the backwash nozzles, they are moved around toward the stagnant soil accumulator sump. The sump is located away from the accumulator channel water inlet and therefore, more isolated and stagnant, allowing soil to settle. This is due to the fact that water and soil lose velocity as they approach the accumulator sump while most of the water escapes through the screen. The accumulator sump can be configured more compact when using the shallow accumulator channel of the present invention. The physical configuration of the system reduces water held in the accumulator by 60% or greater.